Astigmatism Nomogram

Buzard Incisional Astigmatism Nomograms

There are three basic incisional astigmatism nomograms presented here. Again the specific parameters and uses of these nomograms are extremely important. These nomograms are published in three basic locations, “Surgical Management of Astigmatism”, Buzard KA: Medical Cornea–Corneal and Refractive Surgery, edited by Richard E. Selser, Jr., Kugler Publications,(New Orleans Academy of Ophthalmology; February 26-28, 1993), pp 87-99, “Clinical results of arcuate incisions to correct astigmatism”; Buzard, Laranjeira and Fundingsland in The Journal of Cataract and Refractive Surgery, vol22, #8, p1062 Oct 1996 and in the book on Astigmatism written by Dr Buzard and Troutman, “Corneal Astigmatism: Etiology, Prevention, and Management”, CV Mosby, published 1992, Richard Troutman, M.D., Kurt Buzard, M.D. Two basic paradigms are presented. The T-cut nomograms use short (2-2.5mm) incisions and vary the optical zone to obtain different effects. The arcuate nomograms use a constant 7mm optical zone and vary the length to obtain different effects. All astigmatic incisions are made shallow with 80% depth incisions. Thefirst nomogram is to be used specifically with RK and one can see that for a given optical zone, more effect will be obtained in a cornea with an RK than for T-cuts performed in a cornea without RK as seen in the second nomogram for virgin (without RK) corneas. Finally the last nomogram is for arcuate incisions and used for larger degrees of astigmatism, of particular use after cataract surgery. Note no incisions are made larger than 90 degrees and in fact incisions larger than 60 degrees are discouraged as a primary operation in patients older than 65 years old.

 

Buzard T-Cut Nomogram with Radial Keratotomy

___________________________

T-Cuts 2 mm long

One pair of T-Cuts

AGE

Optical

Zone

20

25

30

35

40

45

50

55

60

65

70

5.0

2.55

2.78

3.00

3.23

3.45

3.68

3.90

4.13

4.35

4.58

4.80

5.5

1.70

1.85

2.00

2.15

2.30

2.45

2.60

2.75

2.90

3.05

3.20

6.0

0.85

0.93

1.00

1.08

1.15

1.23

1.30

1.38

1.45

1.53

1.60

7.0

0.64

0.69

0.75

0.81

0.86

0.92

0.98

1.03

1.09

1.14

1.20

To be used with or after radial keratotomy

 

 

 

BUZARD T-CUT NOMOGRAM

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T-CUTS 2 – 2.5 MM LONG

One Pair of T-Cuts

AGE

Optical

Zone

20

25

30

35

40

45

50

55

60

65

70

75

80

5.00

1.70

1.85

2.00

2.15

2.30

2.45

2.60

2.75

2.90

3.05

3.20

3.35

3.50

5.50

1.28

1.39

1.50

1.61

1.72

1.84

1.95

2.06

2.17

2.28

2.40

2.51

2.62

6.00

.85

.93

1.00

1.08

1.15

1.23

1.30

1.38

1.45

1.53

1.60

1.68

1.75

7.00

           

.78

.85

.93

1.00

1.08

1.15

1.23

VIRGIN CORNEA

(No Previous Operation on Cornea)

 

 

 

 

BUZARD ARCUATE NOMOGRAM

___________________________

7MM OPTICAL ZONE

AGE

DEGREE OF ARC

20

25

30

35

40

45

50

55

60

65

70

75

80

45

1.70

1.85

2.00

2.15

2.30

2.45

2.60

2.75

2.90

3.05

3.20

3.35

3.50

60

2.55

2.78

3.00

3.23

3.45

3.68

3.90

4.13

4.35

4.58

4.80

5.03

5.25

90

3.40

3.70

4.00

4.30

4.60

4.90

5.20

5.50

5.80

6.10

6.40

6.70

7.00

VIRGIN CORNEA

(No Previous Operation on Cornea)